1. Field of the Invention
The present invention relates to a liquid discharge head substrate, a liquid discharge head, and a liquid discharge apparatus. More particularly, the present invention relates to a circuit configuration and a circuit layout of a liquid discharge head substrate having a multi-ink channel capable of supplying a plurality of kinds of liquid (e.g., ink) to the same liquid discharge head substrate.
2. Description of the Related Art
Liquid discharge apparatuses are configured to record information on a recording medium by discharging recording ink from a plurality of fine discharge ports of a liquid discharge head according to a recording signal. The liquid discharge apparatuses have advantages of non-contact printing onto recording media, such as paper, easy colorization, and silent operation.
An inkjet method for performing recording utilizing thermal energy is described below as an example of the liquid discharge method. The liquid discharge head used for the inkjet method is provided with recording elements (e.g., heaters) corresponding to discharge ports, from which liquid such as ink is discharged. Electric current is applied to the heaters to cause the heaters to generate heat. Thus, ink is heated to discharge ink droplets for recording.
To obtain a higher-resolution recorded image, it is desired that the number of heaters is increased, and that the heaters are disposed at a high density in the liquid discharge head. Also, to reduce costs of recording heads, it is desired that inkjet head substrates (hereunder referred to as element substrates), on each of which heaters and circuits are provided, are miniaturized. Generally, a semiconductor wafer is used as an element substrate. Accordingly, to reduce the cost of the element substrate, it is useful to reduce the area of an element substrate to increase the number of element substrates that can be produced from a single wafer.
A method for reducing the increase of the area of an element substrate even when the number of recording elements increases is discussed in U.S. Patent Application Publication No. US 2005/0134620 A1. FIG. 9 illustrates a circuit diagram of a heater array (array of heaters) 110 discussed in U.S. Patent Application Publication No. US 2005/0134620 A1. FIG. 10 illustrates a layout of an element substrate discussed also in U.S. Patent Application Publication No. US 2005/0134620 A1. According to the method discussed in U.S. Patent Application Publication No. US 2005/0134620 A1, at least one of an element selection circuit and a driving selection circuit is disposed adjacent to a driving circuit of each group having a predetermined number of adjacent recording elements. More specifically, a latch circuit 104, which holds recording data with the bit number corresponding to the number of groups to be time-division driven, and a shift register 105 are disposed adjacent to logic circuits 114 of each of the groups corresponding to each heater array 110, so that sets of the latch circuit 104 and the shift register 105 are arranged to extend in the longitudinal direction of an ink supply port 109.
Furthermore, Japanese Patent Application Laid-Open No. 11-245409 discusses a method for reducing the number of drive circuits to one-half of the number of arrays of heating elements by causing a single drive circuit, which is connected in parallel to two adjacent arrays of heating elements, to perform time-division driving of the two adjacent arrays of heating elements, thus miniaturizing a recording head.
The method discussed in U.S. Patent Application Publication No. US 2005/0134620 A1 can implement a liquid discharge head capable of high-quality recording with a multi-ink channel configuration obtained by providing a plurality of ink supply ports in an element substrate. However, circuits, such as shift registers, are disposed corresponding to each heater array along the longitudinal direction of an ink supply port. Consequently, there is a limit to reduction in the distance between adjacent ink supply ports.
On the other hand, according to the method discussed in Japanese Patent Application Laid-Open No. 11-245409, adjacent two heater arrays are driven by a single drive circuit and drive signals for a single heater array. With this configuration, the adjacent two heater arrays cannot simultaneously be driven. Consequently, it is difficult to concurrently implement both high-speed recording and high-quality recording.